The invention relates to a valve construction wherein solenoid excitation of an elongate magnetostrictive core element is relied upon to actuate a valve for control of fluid flow, as for controlling the flow of a pressure fluid from an upstream source to an outlet for downstream storage or utilization at reduced pressure.
Pending application Ser. No. 309,776, filed Sep. 21, 1994 now U.S. Pat. No. 5,501,425 issued Mar. 26, 1996 describes several embodiments of magnetostrictive valves of the character indicated, with specific utility and application to spacecraft, wherein the valve is necessarily of normally closed variety and a very high seating force is desired, to provide positive sealing and very low leakage under lock-up (i.e. valve-closed) conditions. Pressurized propellant gas for maneuvering must be conserved at all costs, relying upon valves with superior (i.e., very low) leakage resistance under lock-up conditions, yet offering fast response to instant demand. Thus, shut-off, isolation, low friction, mechanical simplicity and small size are important considerations in a valve of the character indicated. A magnetically latching and magnetically actuated valve of the nature described in U.S. Pat. No. 3,814,376 or in pending application Ser. No. 08/184,484 now U.S. Pat. No. 5,375,811 issued Dec. 27, 1994 has properties approaching the desired low-leakage of a valve-closed condition, but the time constant for valve actuation (opening or closing) is greater than would be desired, and the seating force is less than desired.
The disclosure of said pending application Ser. No. 309,776 is hereby incorporated by reference, and it suffices here to note that all of the disclosed embodiments of said application relied upon a central cylindrical core element of magnetostrictive material, forming part of a toroidal path of magnetic flux, wherein the toroidal path surrounds an excitation winding. One axial end of the core element has reference to the valve housing, and the other axial end is poised to drive an actuating stem into abutment with and valve-opening displacement of a valve member which is otherwise spring-loaded into its closed relation of engagement with a valve seat. Disc washers or Belleville springs are utilized for axial-force preloading and to center component parts for minimum friction and/or mechanical hysteresis, but the constructions are more than is believed strictly necessary. Moreover, inlet and outlet parts serve valve-chamber regions at one axial end of magnetostrictive actuating system.